Short communicationRapid and simultaneous determination of acidity and salt content of pickled vegetable brine by using thermal infrared enthalpimetry

- One step is required for analysis by the simple addition of sample on reagents.
- Total acidity and salt content could be determined simultaneously.
- No sample preparation (e.g., dilution, filtration, distillation) is need.
- Analysis time was reduced and throughput increased at least one order of magnitude.
- Easy adaption for both laboratory and industrial field.

A rapid and high throughput method was developed for determination of the total acidity and salt content of brine from pickled vegetables (containing cauliflower, cucumber, carrot and onion) using thermal infrared enthalpimetry (TIE). An infrared camera was combined with disposables microplates to perform enthalpimetric analysis using a multichannel pipette for reagent addition. Microplates were charged with a stoichiometric excess of reagents (NaOH and AgNO3) with the subsequent addition of the sample. The temperature rise of reactions was measured instantaneously and the total acidity and salt content of brine were obtained simultaneously by comparison with calibration curves. For total acidity determination, calibration curves were established with both lactic and acetic acids with no difference between them. An interference study was performed and interferences of brine composition were not observed. The results obtained by TIE analysis were in agreement with the results of recommended methods in official compendia (between 94% and 103%). Using TIE, 3 min were enough to perform 12 measurements of both total acidity and salt content, reaching 240 measurements per hour. For the same number of measurements by conventional method (titration) one or two days were required, which shows the feasibility of the proposed method for rapid analysis.